A general construction of a valve shaft seal is disclosed in German Offenlegungsschrift No. DE 39 02 518 A1. The disclosed valve shaft seal is constructed with a reinforcing ring having a radially extending end section, with the reinforcing ring being supported on the component which carries the valve shaft seal. The disclosed valve shaft seal is also provided with a valve spring. To support the valve spring, a spiral spring is ground off at one end so that it presents a good resting surface on the radially extending end section of the reinforcing ring. The radially extending end section changes with a radius into the cylindrical section extending over a certain length of the reinforcing ring which forms a centering mechanism for the valve spring.
However, it has been found that problems can arise with this construction in that the sharply ground end of the valve spring in the radius area that is in the transitional area between the radially extending end section of the reinforcing ring and the cylindrical section of the reinforcing ring can press in and possibly damage the surface of the reinforcing ring. This can in turn lead to the formation of cracks in the reinforcing ring or break-offs from the reinforcing ring. As a result, damage of the valve shaft seal can occur which may lead to premature failure of the seal.
A need thus exists for a valve shaft seal of the type mentioned above which provides a reliable support of the valve spring on the radially extending end section of the reinforcing ring and a clean centering of the valve spring by the cylindrical section of the reinforcing ring, but which nevertheless reduces the likelihood that the valve spring sharply ground in the end area will cause damage to the reinforcing ring.